1. Field of the Invention
The present invention relates to a hose-connector assembly used for fuel transportation or other purposes in automotive vehicles; which assembly includes a hose with an outer protector tube and a connector. This invention is also concerned with a method of producing such a hose-connector assembly.
2. Discussion of the Related Art
A hose made of a rubber material has been conventionally used as a fuel transporting hose for automotive vehicles. Recently, however, there is a growing tendency of using a resin tube such as a tube made of nylon or other hard resin material, which has high gasoline impermeability and which is less expensive than a rubber hose. This tendency of using a resin tube in place of a rubber hose applies to an air hose and hoses having other applications in automotive vehicles.
The hose using a resin tube is required to be protected against an external mechanical impact or heat, by an outer rubber protector tube or layer which covers the inner resin tube. For instance, the outer rubber protector tube is made of ethylene propylene rubber or other EP rubber material which has high degrees of weather and heat resistances. In particular, the outer rubber protector tube is essential for the fuel transporting hose, in order to reduce the heat transfer to the fuel within the resin tube, upon generation of a flame for some reason or other.
For installing the fuel transporting hose, for example, on an automotive vehicle, a tubular connector is partly press-fitted into one or both of the opposite end portions of the hose, so that a pipe or other member is connected to each connector. Typically, a tubular connector of a so-called xe2x80x9csingle-action engagementxe2x80x9d type is generally used, for permitting easy, quick connection of the pipe or other member to the hose, with a single action of pushing the pipe into the end portion of the hose.
An example of the recently developed, widely used hose-connector assembly for fuel transportation or other purposes used for automotive vehicles is illustrated in FIG. 4. This hose-connector assembly includes an inner resin tube 1, an outer rubber protector tube 2 which covers the outer surface of the inner resin tube, and a tubular connector 3 which is inserted at one end thereof into each of the opposite end portions of the resin tube 1 so that a suitable member is connectable to the connector 3 at the other end.
The known hose-connector assembly shown in FIG. 4 is produced by preparing the resin tube 1 and the rubber protector tube 2 separately from each other, and press-fitting the rubber protector tube 2 onto the outer circumferential surface of the inner resin tube 1. This manner of assembling the resin tube 1 and the rubber protector tube 2 into the hose inevitably causes the opposite end portions of the inner resin tube 1 to extend from the opposite ends of the rubber protector tube 2. This tendency is remarkable particularly where the resin tube 1 is a bent tube. In this case, a relatively large clearance or gap is likely to be present between each end portion of the rubber protector tube 2 and the outer surface of the inner resin tube 1.
Thus, each end portion 1a of the resin tube 1 of the known hose-connector assembly is exposed, and is not covered and protected by the outer rubber protector tube 2. The exposed end portion 1a is relatively likely to be overheated and damaged in a short time upon generation of a flame near the exposed end portion 1a, for instance. Accordingly, the rubber protector tube 2 cannot serve its assigned function of protecting the resin tube 1 against heat or flame from which the fuel flowing in the resin tube 1 must be isolated.
Another problem with the known hose-connector assembly is that it is difficult to securely attach the tubular connector 3 at its nipple portion 3a to the corresponding end portion of the hose 1, 2, since the end portion 1a of the resin tube 1 is exposed and is not covered by the corresponding end portion of the rubber protector tube 2. Namely, the hose cannot be held with a suitable clamping tool being fitted on the outer surface of the end portion of the rubber protector tube 2 when the nipple portion 3a is press-fitted into the exposed end portion 1a of the resin tube 1, so that the exposed end portion 1a of the resin tube 1 tends to be easily buckled upon press-fitting of the nipple portion 3a into the exposed end portion 1a, which is not externally supported by the outer rubber protector tube 2.
A static electricity may be generated due to a friction between the fuel and the resin tube 1 in which the fuel flows. To avoid the generation of a spark due to the static electricity, it is required that the static electricity be discharged from the resin tube 1 through a pipe (usually a metallic male member) to which the tubular connector 3 in the form of a male member is connected.
To meet the above requirement, the tubular connector 3 is required to be made of a metallic material or an electrically conductive resin material, while the resin tube 1 to which the connector 3 is connected is required to be electrically conductive. On the other hand, however, the resin tube 1 is required to have a high degree of gasoline impermeability, and is therefore difficult to be made solely of an electrically conductive resin. That is, the resin tube 1 is required to include not only an inner layer of an electrically conductive resin such as electrically conductive ETFE (copolymer of ethylene and tetrafluoroethylene), but also an outer layer made of nylon, for example. This results in an increase in the cost of manufacture of the fuel transporting hose.
It is therefore a first object of the present invention to provide a relatively inexpensive hose-connector assembly having an inner resin tube and an outer rubber protective tube and a tubular connector, which assembly has sufficiently high degrees of weather and heat resistances and which are less likely to be buckled upon press-fitting of the connector to the resin tube.
An optional object of the invention is to provide a hose-connector assembly which permits static electricity to be discharged from the resin tube through the connector.
A second object of this invention is to provide a method suitable for producing such a hose-connector assembly.
The first object may be achieved according to a first aspect of this invention, which provides a hose-connector assembly comprising an inner resin tube having an outer circumferential surface and opposite end portions, an outer rubber protector tube which covers an outer circumferential surface of the inner resin tube over an entire length of the inner resin tube, and a tubular connector having opposite end portions one of which is press-fitted in each of at least one of opposite end portions of the inner resin tube.
In the hose-connector assembly of the present invention constructed as described above, the outer circumferential surface of the inner resin tube is covered and protected by the outer rubber protector tube, over the entire length of the inner resin tube, so that the hose exhibits increased degrees of heat and weather resistances even at the opposite end portions of the inner resin tube. In particular, the end portions of the inner resin tube covered by the outer rubber protector tube are highly protected from a flame possibly generated near the end portions of the resin tube, where the hose-connector assembly is used on an automotive vehicle, for instance.
The present hose-connector assembly wherein the end portions of the inner resin tube are externally protected by the end portions of the outer rubber protector tube has another advantage that the hose can be held by a suitable clamping tool fitted on the outer surface of the end portion of the outer rubber protector tube when the end portion of the tubular connector is press-fitted into the end portion of the inner resin tube. Accordingly, the end portion of the inner resin tube will not be buckled when the connector is attached to the end portion of the resin tube.
The end face of the end portion of the outer rubber protector tube which corresponds to the above-indicated one end portion of the tubular connector may be substantially flush with the end face of the corresponding end portion of the inner resin tube in a longitudinal direction of said tubes. In this case, the outer circumferential surface of the inner resin tube and the inner circumferential surface of the outer rubber protector tube may be bonded together by an adhesive agent.
Alternatively, the end portion of the outer rubber protector tube which corresponds to the above-indicated one end portion of the tubular connector may extend beyond the end face of the corresponding end portion of the inner resin tube in a direction toward a retainer portion of the tubular connector, so that the above-indicated one end portion of the outer rubber protector tube is held in contact with the outer circumferential surface of the tubular connector. In this instance, the outer rubber protector tube may be formed on the outer circumferential surface of the inner resin tube in the absence of an adhesive agent therebetween.
Where the outer rubber protector tube has an end portion extending from the end face of the corresponding end portion of the inner resin tube, it is preferable that at least the tubular connector, and preferably both of the tubular connector and the outer rubber protector tube be electrically conductive or include an electrically conductive portion. In this case, static electricity generated by the inner resin tube may be discharged through the electrically conductive connector to a member which is to be connected to the hose through the connector. This arrangement, which achieves the optional object of the invention indicated above, assures improved safety of the hose-connector assembly during its use, without using the resin tube including an electrically conductive layer, which increases the cost of manufacture of the hose. However, the inner resin tube may include such an electrically conductive layer, such as an electrically conductive nylon or ETFE inner layer.
The second object indicated above may be achieved according to a second aspect of this invention, which provides a method of producing a hose-connector assembly of the present invention constructed as described above, the method comprising the steps of: forming by extrusion an inner resin tube layer having a length sufficient to provide a plurality of inner resin tubes; forming by extrusion an outer rubber protector tube layer having substantially the same length as the inner resin tube layer, using an unvulcanized rubber material, such that an outer circumferential surface of the inner resin tube layer is covered by the outer rubber protector tube layer over an entire length of the inner resin tube layer, to obtain a laminar tubular blank consisting of the inner resin tube layer and the outer rubber protector tube layer; cutting the laminar tubular blank into pieces each of which provides a hose consisting of the inner resin tube and the outer rubber protector tube; and press-fitting the above-indicated one end portion of the tubular connector in each of at least one of the opposite end portions of the inner resin tube.
In the present method, the hose consisting of the inner resin tube and the outer rubber protector tube is prepared by cutting the laminar tubular blank obtained by forming by extrusion the inner resin tube layer and the outer rubber protector tube layer such that the outer circumferential surface of the inner resin layer tube is covered by the outer rubber protector tube layer over the entire length of the inner resin tube layer. Accordingly, the inner resin tube of the hose is covered by the outer rubber protector tube over the entire length of the inner resin tube. Therefore, the hose-connector assembly including the hose has substantially the same advantages as described above with respect to the hose-connector assembly.
The unvulcanized rubber material of the outer rubber protector tube layer may be subjected to a vulcanization process, before the laminar tubular blank including the vulcanized outer rubber protector tube layer is cut into pieces. Alternatively, the unvulcanized rubber material of a rubber protector tube portion of each of the pieces which have been obtained by cutting the laminar tubular blank may be subjected to a vulcanization process.
When the above-indicated one end portion of the tubular connector is press-fitted in each of at least one of the opposite end portions of the inner resin tube, the inside diameter of each of at least one of the opposite end portions of the inner resin tube may be increased.
The hose may be given a desired curved configuration by softening the hose by heating thereof before or after the above-indicated one end portion of the tubular connector is press-fitted in each of at least one of the opposite end portions of the inner resin tube.
The outer circumferential surface of the inner resin tube layer may be coated with an adhesive agent, so that an inner circumferential surface of the outer rubber protector tube layer is bonded with the adhesive agent to the outer circumferential surface of the inner resin tube layer, so as to assure that an end portion of the outer rubber protector tube which corresponds to the above-indicated one end portion of the tubular connector is substantially flush with that of the corresponding end portion of the inner resin tube in a longitudinal direction of the tubes.
The outer rubber protector tube layer may be formed by extrusion on the outer circumferential surface of the inner resin tube layer, in the absence of an adhesive agent on the outer circumferential surface of the inner resin tube layer, so that an end portion of the outer rubber protector tube which corresponds to the above-indicated one end portion of the tubular connector extends beyond an end face of the corresponding end portion of the inner resin tube in a direction toward the other end portion of the tubular connector, as a result of relative movement of the inner resin tube and the outer rubber protector tube while the end portion of the tubular connector is press-fitted in each of at least one of the opposite end portions of the inner resin tube.